Moffett said the threat was one of many that Sgt. Timothy Cooper directed at him over the years, a vendetta he alleges was motivated by Cooper's ties to a secret deputy clique.

The sergeant's allegations — of public threats made with impunity, of deputies divided by cliques, of a code of silence — mirror the challenges facing the Sheriff's Department as it tries to change its culture amid a jail abuse scandal and intensifying outside scrutiny.

The case was taken to the department's discipline committee, with a recommendation that Cooper be demoted. But the group of executives opted for a more lenient punishment: a 15-day suspension, sources said.

Sheriff Lee Baca questioned the committee's decision when he learned about it, according to sources familiar with the case, who spoke on condition of anonymity because it involves confidential discipline.

Earlier this month, Baca dissolved the committee and created a new system in which he plays a larger role in determining significant punishment.

The move comes after Baca, and other officials, said in recent months that the sheriff often was kept in the dark by his top executives about bad behavior inside the department.

In an interview, Baca said he could not comment on the gun-pointing case because of privacy constraints, but he said that his streamlining of the department's discipline structure would ensure that in the future "there aren't any gaps in the decision-making process."

Moffett, who is suing the department, said that for years he stayed mum about the abuse because he feared being labeled a snitch and the possibility of retaliation from others inside the Sheriff's Department. But he came forward after that morning at the station in May 2009.

His allegations were investigated internally by the department. Prosecutors declined to file charges against Cooper, saying that he could claim that his actions were "just another in an ongoing series of pranks."

A district attorney's memo obtained by The Times provides details about the sheriff's criminal investigation into what happened:

Moffett told authorities he pulled into the employee lot at 4:30 a.m. As he walked toward the station, he said, Cooper pulled up in a sheriff's patrol SUV, revved the engine and smirked. Cooper then allegedly drove toward him slowly, stopping just a few feet short of striking Moffett.

"What are you going to do?" Moffett recalled saying. "Run me over?"

Cooper, he said, nodded his head and smiled.

Surveillance video shows the SUV proceeding at a steady pace and stopping within five feet of Moffett, the district attorney's memo states.

Later, inside the station, Cooper walked by Moffett, unsnapped his holster, and again smiled and nodded. He was standing just behind another station supervisor when he brandished his gun.

That supervisor, Sgt. Douglas Iketani, told investigators that he believed Cooper pointed the gun in Moffett's general direction.

Moffett told investigators that Cooper proceeded to close one eye as if he were aiming before allegedly mouthing his death threat, according to the prosecutor's memo.

That kind of harassment, Moffett said, had begun several years earlier when the two were both assigned to a gang investigations unit out of the sheriff's Century station. Cooper and other members of the unit started at the Century station, according to a prosecutor's memo, but Moffett came from the Lakewood station. Cooper, Moffett said, taunted him for not being a "real" deputy.

On one occasion, Moffett said the two were patrolling a rough neighborhood and stopped a drug suspect when Cooper drove off without him. On several occasions, he said, Cooper and others assaulted him inside the station elevator. Cooper, he said, also had pointed his gun at him before — between 15 and 40 times.

A friend of Moffett's, who is a local prosecutor, confirmed to a sheriff's investigator that Moffett had confided in him about the abuse at the time.

There is no indication in the memo that Cooper was interviewed for the criminal investigation.

In deciding against filing charges, Head Deputy Dist. Atty. Sergio Gonzalez noted in the prosecution memo that Moffett's allegations involved behavior going back years that was sometimes witnessed by other deputies who looked on and laughed.